Films with skin layers incorporating polyesters are known. Such films are widely used in the packaging industry. Generally, the polyester skin layers are inexpensive, clear, offer high surface energy, and are stable in orientation processes.
U.S. Pat. No. 5,324,467 to Anderson describes coextrusion or extrusion coating processes for the preparation of an oriented multi-layer laminate film, consisting of at least three layers, including a polypropylene layer, an adhesive layer of polar modified polyolefin, and a glycol or acid modified copolyester layer. The multi-layer film is prepared by uniaxially or biaxially stretching castings. It is disclosed that the film has good heat sealability and high gas barrier.
U.S. Pat. No. 5,637,366 to Davis, et al. and U.S. Pat. No. 6,221,191 to Davis, et al. disclose biaxially oriented polypropylene core layer films with multiple layer film cap layers. The cap layer is laminated or coated onto the core layer. The cap layer includes at least one polyester layer and at least one tie layer interposed between the polyester layer and the PP core. The cap layer is provided on a machine direction oriented uniaxially oriented polypropylene core layer. The resulting composite is stretched in a transverse direction.
U.S. Pat. No. 6,472,081 to Tsai, et al. discloses an oriented multi-layer film combination including a propylene homopolymer or copolymer core layer, a metallizable skin layer including a material selected from an ethylene-vinyl alcohol copolymer (EVOH), poly(vinyl alcohol) (PVOH), and polyester. An adhesive tie layer made from a material selected from a maleic anhydride modified propylene homopolymer or copolymer, a high density polyethylene (HDPE), and an ethylene-vinyl acetate (EVA) copolymer. The adhesive tie layer is disposed between the core layer and the skin layer.
U.S. Pat. No. 6,027,776 to Mueller discloses a multi-layer film incorporating an interior layer of ethylene/alpha-olefin copolymer; a first exterior layer of a material selected from a propylene homopolymer or copolymer, a propylene homopolymer or copolymer blended with an elastomer, HDPE, and a copolyester. A second exterior layer includes a material selected from a polyamide, a copolyamide, polyester, copolyester, HDPE, PP, propylene/ethylene copolymer, and polycarbonate. A first adhesive layer is provided between the interior layer and the first exterior layer while a second adhesive layer is provided between the interior layer and the second exterior layer. The adhesive layers are anhydride-modified ethylene/methyl acrylate copolymers. It is disclosed that this film is used to produce flexible pouches for the packaging and administration of medical solutions.
U.S. Pat. No. 6,663,974 to Kelch, et al. discloses a non-oriented multi-layer film with a polyolefin core incorporating 40 wt. % or less of homogeneous ethylene/alpha-olefin. A modified polyolefin tie layer is provided on each side of the core layer with an adhesive layer on at least one tie layer. The adhesive layer contains a polar-modified polyolefin and a polyester, copolyester, or polyester and copolyester blend. It is disclosed that this multi-layer film has utility as a protective coating for metal surface.